The present invention relates generally to shock absorbers having a unique rebound valve. More particularly, the present invention relates to a shock absorber having a rebound valve defined by a valve assembly that combines both the normal valving for the shock absorber and a blow-off function.
Shock absorbers are used in connection with automotive suspension systems and other suspension systems to absorb unwanted vibrations which occur during movement of the suspension system. In order to absorb this unwanted vibration, automotive shock absorbers are generally connected between the sprung (body) and unsprung (suspension) masses of the automobile.
The most common type of shock absorbers in automobiles is the dashpot type in which a piston is located within a pressure tube and is connected to the sprung mass of the vehicle through a piston rod. The piston divides the pressure into an upper working chamber and a lower working chamber. Because the piston, through valving, has the ability to limit the flow of damping fluid between the upper and lower working chambers within the pressure tube when the shock absorber is compressed or extended, the shock absorber is able to produce a damping force which counteracts the vibrations which would otherwise be transmitted from the unsprung mass to the sprung mass. In a dual tube shock absorber, a fluid reservoir is defined between the pressure tube and the reserve tube. A base valve is located between the lower working chamber and the fluid reservoir to produce a damping force which also counteracts the vibration which would otherwise be transmitted from the unsprung portion to the sprung portion of the automobile.
Automotive shock absorbers are generally provided with bleed orifices which allow the restricted flow of damping fluid from the upper side of the piston, which is know as the rebound side, and the lower side of the piston, which is known as the compression side. These bleed orifices provide the shock absorber with a portion of its damping characteristic. Automotive shock absorbers also may include a blow off valve of some type. The blow off valve is normally in a closed position. However, when fluid pressure within the pressure cylinder reaches a predetermined level, the blow off valve opens reducing considerably the restriction of damping fluid flow between the two sides of the piston.
Various designs in the prior art combine the conventional piston valving with a blow off valve. For example, U.S. Pat. No. 4,721,130, issued on Jan. 26, 1988, to Hayashi for xe2x80x9cValve Structure of Hydraulic Bufferxe2x80x9d discloses a valve structure used in a hydraulic buffer. A valve body is used for opening and closing ports in the piston. As the piston rod is extended, a free end of the valve body deflects about a first fulcrum point to allow liquid to pass. When the piston is moving at a high rate of speed and the force of the liquid passing through the port exceeds the pre-load set by the spring, the spring seat is depressed so that more liquid flows through the port while deflecting the valve body about a second fulcrum point.
Additionally, U.S. Pat. No. 2,717,058, issued to Brundreit on Sep. 6, 1955 for xe2x80x9cShock Absorber Control Valvexe2x80x9d discloses a shock absorber control valve for controlling restricted flow of hydraulic fluid between opposite ends of a pressure tube. A valve disk flexes upwardly against a rigid retainer plate as permitted by the angularity of the face portion of the plate. As the requirement for fluid flow increases, the valve member and the retainer are moved against the compression spring to change the fluid flow rate.
While these prior art systems have performed acceptably, they are relatively complex and they fail to produce optimum results in the terms of efficiency and cost. The continued development of shock absorbers includes the development of systems which combine the flexing disk function of a rebound valve with the blow off function in a system that is less complex and less expensive while providing the necessary damping acquirements.
The present invention provides the art with a shock absorber that includes a flexing disc assembly which combines the flexing disc function of a rebound valve with the blow off function. The shock absorber of the present invention utilizes a flexing disc assembly for allowing the passage of fluid between the two sides of the piston in the pressure tube. The fluid discs are held against the piston body by a spring and a washer. The spring and washer are retained and thus biased towards the valve discs by a nut. The nut is threaded onto the end of the piston rod. A spacer limits the travel of the nut thus controlling the amount of spring preload while eliminating tolerance build up and over compression of the discs.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.